Toronto: Feeling stressed in the presence of strangers curbs the ability to express empathy - the capacity to share and feel another individual's emotions - in animals and humans alike, says a study.

"The research identifies a reason for the empathy gap and answers the vital question of how do we create empathy between strangers," said psychology professor Jeffrey Mogil from McGill University in Canada.

In the new study, Mogil and his team compared the reactions of undergraduate students to painful stimuli in various scenarios.

The student participants were asked to submerge their arm in ice-cold water and rate their pain.

Their pain scores remained the same whether they experienced the pain alone or sitting across from a stranger.

However, the pain actually increased when a friend happened to sit across them.

"It would seem like more pain in the presence of a friend would be bad news, but it is a sign that there is strong empathy between individuals - they are indeed feeling each other's pain," Mogil added.

To further test this "social stress" barrier to empathy between strangers, student participants paired with strangers were given the opportunity to play "Rock Band" prior to the experiment.

After only 15 minutes of playing "Rock Band" together, these strangers showed empathy toward one another when they experienced the pain from exposure to ice water.

"It turns out that even a shared experience that is as superficial as playing a video game together can move people from the 'stranger zone' to the 'friend zone' and generate meaningful levels of empathy," Mogil said.

This demonstrates that basic strategies to reduce social stress could start to move us from an empathy deficit to a surplus, said the study that appeared in the journal Current Biology.